Cod Liver Oil: Vitamin A and D Limits, Benefits and Side Effects

Cod liver oil is oil pressed from the livers of cod, and it differs from most omega-3 supplements in one important way: besides the omega-3 fats EPA and DHA, it naturally carries large amounts of vitamin A and vitamin D. In USDA data, a single teaspoon supplies about 150% of the Daily Value for vitamin A and more than half the Daily Value for vitamin D. Those vitamins are the reason people once took it, and they are also the main safety issue, because both have official upper limits set by the National Academies. Below are the USDA nutrition numbers, what the NIH Office of Dietary Supplements (ODS) says about the limits, and who should be careful.

Peptide Labs does not sell cod liver oil. This article is general nutrition information, not medical advice.

Cod liver oil nutrition per teaspoon and tablespoon

The table uses the USDA FoodData Central SR Legacy entry for cod liver oil (FDC 173577). Percent Daily Values (%DV) use the FDA Daily Values printed on labels. Commercial products vary, so the Supplement Facts panel on the bottle, not the USDA average, tells you what a specific product contains.

For context, here is how the same nutrients compare with two ordinary fish servings in USDA data. Salmon delivers a similar amount of vitamin D and more omega-3 than a teaspoon of the oil, with very little vitamin A, while cod fillet itself is lean and low in all three.

Cod liver oil vitamin A and the upper limit

Vitamin A comes in two forms. Preformed vitamin A (retinol and its esters) is found in animal foods and many supplements, while beta-carotene and other carotenoids come from plants. Cod liver oil provides the preformed kind, which the body stores in the liver, so excess can build up over time. According to the ODS vitamin A fact sheet, the Tolerable Upper Intake Level (UL) for preformed vitamin A is 10,000 IU per day for adults, about 333% of the Daily Value, and it is lower for teenagers and much lower for children. The UL covers all animal sources and supplements combined.

Compare that with the table: a USDA tablespoon of cod liver oil holds about 13,600 IU, which is above the adult UL before counting a multivitamin, fortified foods or liver. A teaspoon holds less than half the UL. ODS lists the effects of long-term excess as dry skin, painful muscles and joints, fatigue, depression and abnormal liver tests. If you also eat liver or take a liver supplement, our beef liver supplement guide shows how quickly preformed vitamin A adds up.

ODS also flags two medicine interactions. Retinoid drugs such as acitretin and bexarotene raise the risk of vitamin A toxicity when combined with vitamin A supplements, and orlistat (sold as Alli and Xenical) can lower the absorption of vitamin A and other fat-soluble vitamins; see our alli guide.

Vitamin D in cod liver oil

Fish liver oils are among the richest natural sources of vitamin D, and the ODS vitamin D fact sheet notes that milk fortification starting in the 1930s, along with the use of cod liver oil, made rickets rare in the United States. Today most Americans get vitamin D from fortified foods, fatty fish and sunlight; our vitamin D foods list covers the options.

The UL for vitamin D is 4,000 IU per day from age 9, or 500% of the Daily Value. ODS says vitamin D toxicity almost always comes from supplements, not food or sun. It raises blood calcium, which can cause nausea, vomiting, muscle weakness, loss of appetite, dehydration, excessive thirst and kidney stones, and in extreme cases kidney failure and heart rhythm problems. If you already take a vitamin D product, such as one of the combinations in our vitamin D3 and K2 guide, count the vitamin D in cod liver oil too.

Cod liver oil during pregnancy

This is the most important caution. The ODS vitamin A fact sheet says total intakes of preformed vitamin A above the UL can cause birth defects, including malformations of the eye, skull, lungs and heart. Experts advise women who are or might be pregnant, and those who are breastfeeding, not to take high-strength vitamin A supplements above the UL.

That does not mean every cod liver oil product is off limits, but it does mean the vitamin A on the label has to be added to the vitamin A in a prenatal vitamin and in food. Many prenatal products already contain vitamin A; our prenatal vitamins guide explains what to look for. If you are pregnant or trying to conceive, show the label to your OB-GYN or midwife before using cod liver oil, or ask whether an omega-3 product without vitamin A fits better.

Cod liver oil side effects, fish allergy and blood thinners

Most reported cod liver oil side effects are the same mild ones seen with other omega-3 supplements. The ODS omega-3 fact sheet lists an unpleasant taste, bad breath, heartburn, nausea, stomach discomfort, diarrhea, headache and smelly sweat. Beyond those, a few groups should check first:

• Fish allergy: the FDA lists fish among the major food allergens. Even prescription omega-3 labels state that it is not known whether people with fish or shellfish allergy are at higher risk of a reaction, so ask your allergist before trying a fish-derived oil.
• Warfarin and other anticoagulants: ODS notes that fish oil might prolong clotting times, measured as a higher INR, when taken with warfarin, although most research has not found a significant effect. The package inserts of prescription omega-3 drugs advise periodic INR checks for people on anticoagulants. Tell the clinician who manages your blood thinner before starting.
• Retinoid medicines, orlistat or other vitamin A and D products: see the sections above; the vitamins, not the fat, are the concern here.
• Children: their vitamin A and D upper limits are far lower than adults’ limits, so use only products made for children and only with a pediatrician’s input.

On contaminants, ODS says omega-3 supplements have not been found to contain methyl mercury, because it is removed during processing. Quality still varies, so a third-party seal such as USP or NSF is worth checking; our third-party testing guide explains what each seal does and does not cover.

Cod liver oil benefits: what can be said

The honest summary is that cod liver oil is a concentrated source of three nutrients: EPA and DHA, vitamin A and vitamin D. Research on omega-3 fats in general, covered in our omega-3 guide, mostly tested purified fish or prescription oils, not cod liver oil, and the results for heart and other outcomes have been mixed. We did not find recent large trials of cod liver oil itself, so claims about immunity, joints, skin or mood go beyond the evidence.

For many people the practical question is whether they want the extra vitamins at all. Someone whose diet is low in fish and who gets little sun might value the vitamin D, while someone already taking a multivitamin, a vitamin D product or liver may end up over the limits. Our krill oil comparison covers omega-3 supplements that do not carry vitamin A, and our sibling guide to castor oil covers a very different oil that is also sold as a traditional remedy.

Frequently Asked Questions

Questions about a label? Contact us or read our Buyer’s Guide. Follow the label and ask a healthcare provider or pharmacist before starting a supplement or an over-the-counter remedy, especially if you take medicines, are pregnant or breastfeeding, or have a food allergy. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Last reviewed October 2026.

Related guides: Krill Oil vs Fish Oil: Absorption, Evidence and Safety Compared, Vitamin D Foods: 17 Sources Ranked With USDA Data, Omega-3: Benefits, Foods, Side Effects and Heart Research.